1. Field of the Invention
The invention relates to methods of treating a lung having at least one symptom of reversible obstructive pulmonary disease, and more particularly, the invention relates to devices for transferring energy into airway tissue to at least reduce the ability of the lung to produce at least one of the symptoms of reversible obstructive pulmonary disease. The invention includes additional steps that reduce the ability of the lung to produce at least one of the symptoms of reversible obstructive pulmonary disease and to reduce the resistance to the flow of air through a lung.
2. Brief Description of the Related Art
Reversible obstructive pulmonary disease includes asthma and reversible aspects of chronic obstructive pulmonary disease (COPD). Asthma is a disease in which (i) bronchoconstriction, (ii) excessive mucus production, and (iii) inflammation and swelling of airways occur, causing widespread but variable airflow obstruction thereby making it difficult for the asthma sufferer to breathe. Asthma is a chronic disorder, primarily characterized by persistent airway inflammation. Asthma is further characterized by acute episodes of additional airway narrowing via contraction of hyper-responsive airway smooth muscle.
The reversible aspects of COPD generally describe excessive mucus production in the bronchial tree. Usually, there is a general increase in bulk (hypertrophy) of the large bronchi and chronic inflammatory changes in the small airways. Excessive amounts of mucus are found in the airways and semisolid plugs of mucus may occlude some small bronchi. Also, the small airways are narrowed and show inflammatory changes. The reversible aspects of COPD include partial airway occlusion by excess secretions and airway narrowing secondary to smooth muscle contraction, bronchial wall edema and inflation of the airways
In asthma, chronic inflammatory processes in the airway play a central role in increasing the resistance to airflow within the lungs. Many cells and cellular elements are involved in the inflammatory process, particularly mast cells, eosinophils T lymphocytes, neutrophils, epithelial cells, and even airway smooth muscle itself. The reactions of these cells result in an associated increase in the existing sensitivity and hyper-responsiveness of the airway smooth muscle cells that line the airways to the particular stimuli involved.
The chronic nature of asthma can also lead to remodeling of the airway wall (i.e., structural changes such as thickening or edema) which can further affect the function of the airway wall and influence airway hyper-responsiveness. Other physiologic changes associated with asthma include excess mucus production, and if the asthma is severe, mucus plugging, as well as ongoing epithelial denudation and repair. Epithelial denudation exposes the underlying tissue to substances that would not normally come in contact with them, further reinforcing the cycle of cellular damage and inflammatory response.
In susceptible individuals, asthma symptoms include recurrent episodes of shortness of breath (dyspnea), wheezing, chest tightness, and cough. Currently, asthma is managed by a combination of stimulus avoidance and pharmacology.
Stimulus avoidance is accomplished via systematic identification and minimization of contact with each type of stimuli. It may, however, be impractical and not always helpful to avoid all potential stimuli.
Asthma is managed pharmacologically by: (1) long term control through use of anti-inflammatories and long-acting bronchodilators and (2) short term management of acute exacerbations through use of short-acting bronchodilators. Both of these approaches require repeated and regular use of the prescribed drugs. High doses of corticosteroid anti-inflammatory drugs can have serious side effects that require careful management. In addition, some patients are resistant to steroid treatment. The difficulty involved in patient compliance with pharmacologic management and the difficulty of avoiding stimulus that triggers asthma are common barriers to successful asthma management.
Asthma is a serious disease with growing numbers of sufferers. Current management techniques are neither completely successful nor free from side effects.
Accordingly, it would be desirable to provide an asthma treatment which improves airflow without the need for patient compliance.
In addition to the airways of the lungs, other body conduits such as the esophagus, ureter, urethra, and coronary arteries, are also subject to periodic reversible spasms that produce obstruction to flow.